Ureidopyrazoles defoliants

ABSTRACT

Certain ureidopyrazoles, such as 5-(3-phenylureido)-1,3dimethylpyrazole, 5-(3-(2-fluorophenyl)ureido)-4-chloro-1,3dimethylpyrazole, and 5-(3-(3-fluorophenyl)ureido)-1,3dimethylpyrazole, are effective as plant growth modifiers. The ureidopyrazoles are particularly useful as defoliants on cotton, soybean, and dry bean plants.

United States Patent 1 1 Brantley 1 UREIDOPYRAZOLES AS DEFOLIANTS [75] inventor: Richard Kirven Brantley, V

Wilmington, Del.

[73] Assignee: E. I. du Pont de Nemours and Company, Wilmington, Del.

[22] Filed: Feb. 25, 1972 [21 1 Appl. No.: 229,555

Related US. Application Data [63] Continuation-impart of Ser. No. 822,001, May 5,

1969, Pat. No. 3,646,059.

Niese et al. 71/74 2,723,274 11/1955 Kaiser et a1 [451 Aug. 28, 1973 3,326,662 6/1967 Toyosato et a1. 71/92 3,385,692 5/1968 Knowles 2,726,150 12/1955 Wolter 71/120 OTHER PUBLICATIONS Dom et al., Redox-Cleavage of Sulfonamides etc., (1965) CA 63 pp. 16330-32 (1965) Primary Examiner-Lewis Gotts Assistant Examiner-G; Hollrah Attorney-Paul R. Steyermark s71 ABSTRACT Certain ureidopyrazoles, such as 5-(3-pheny1ureido)- 1,3-dimethylpyrazole, S-[3-(2-fluoropheny1)ureido1-4- chlorol ,3-dimethylpyrazo1e, and 5-[ 3-( 3- fluoropheny1)ureido]-1,3-dimethylpyrazo1e, are effective as plant growth modifiers. The ureidopyrazoles are particularly useful as defoliants on cotton, soybean, and dry bean plants.

8 Claims, No Drawings UREIDOPYRAZOLES As DEFOLIANTS A a g cRoss REFERENCE TO RELATED APPLICATION N This is a continuation-in-part of my copending application Ser. No. 822,00l, filed May 5, 1969 and now al- 5 lowed and scheduled to issue on Feb. 29, 1972, as US.

Pat. No. 3,646,059.

DESCRIPTION OF THE INVENTION Summary This invention is directed to compounds having the formula:

R R1\ p l{ ll /N-cN l X LY wherein:

R is hydrogen, methyl, ethyl, or phenyl; R is cyclohexyl or Method for Preparing Compounds 0 The compounds of this invention can be prepared according to the following exemplary reaction schemes:

Reaction Scheme 2 Dimerization of a nitrile leads to the formation of an aminonitrile. The nitrile can be dimerized by using methods well known in the art. These methods generally consist of heating the nitrile with or without a solvent in the presence of a strongly alkaline material. Preferred alkalis are alkali and alkaline earth metals as well as their hydrides and alkoxides. The aminonitrile is recovered from the reaction mixture by acidification, filtration, and distillation. The preparation of the aminopyrazole can be carried out by heating the aminonitrile and substituted hydroazine to a temperature of from 50C. to 150C. in the presence of a solvent, such as ethyl alcohol. At this point, halogenation of the 4-position may be performed by reacting the aminopyrazole with a halogenating agent, such as bromine or sulfuryl chloride, in the presence of a solvent, such as water, acetic acid, or carbon tetrachloride, and optionally an acid acceptor, such as sodium acetate or sodium carbonate. The halogenated or nonhalogenated aminopyrazoles can be reacted with either an organic monoisocyanate, and N-(hydrocarbyl)carbamoyl halide, or an N,N-di(hydrocarbyl)carbamoyl halide. The reaction of the aminopyrazole and isocyanate readily occurs in a non-polar solvent, such as benzene. A catalytic amount of a tertiary amine, such as triethyleneamine, often is desirable to catalyze the reaction. The reaction of the aminopyrazole and the carbamoyl halide occurs in an inert solvent, such as benzene. The presence of an acid acceptor in the reaction mixture is desirable. Suitable acid acceptors include tertiary amines, such as pyridine, or an excess of the aminopyrazole. The ureidopyrazole can be recovered by stripping off the solvent and recrystallization of the residue. The halogenation of the 4-position can be carried out subsequent to the reaction of the aminopyrazole and the isocyanate or carbamoyl halide in the same manner as the aminopyrazole.

The compounds of this invention can be considered to be substituted ureas. When R is not hydrogen, the portion of the molecule which contains R and R is derived from an N,N-di(hydrocarbyl)carbamoyl halide. When R is hydrogen, the R portion of the molecule is derived from an isocyanate.

v The following examples illustrate the preparation of the compounds of this invention. Unless otherwise stated, parts are parts by weight.

EXAMPLE 1 Preparation of S-amino-l ,S-dimethylpyrazole Eight and two-tenths parts of B-aminocrotonitrile and 4.5 parts of methylhydrazine are dissolved in 100 parts of ethanol and boiled under reflux for 1.2 hours. The mixture is then subjected to distillation at reduced pressure. The fraction which has a boiling point of 155C. at 32 mm Hg. absolute is -amino-l,3- dimethylpyrazole. When this material is collected and cooled, it crystallizes and shows a melting point of 6970C. The compound has the following structure:

methylpyrazole. Likewise the substitution of ethylhydrazine and phenylhydrazine in the procedure of Ex- An equivalent amount of hydrazine can be substituted for the methylhydrazine used in the procedure of Example 1. This substitution will yield 5-amino-3- ample 1 will lead to the formation of S-amino-l-ethyl- 3-methylpyrazole and S-aminol -phenyl-3- methylpyrazole, respectively.

The above mentioned pyrazoles can be reacted with isocyanates according to the procedures of Examples 3 or 8, infra, to giveappropriate ureidopyrazoles. Thus, if 5-amino-3-methyl-pyrazole is reacted with phenyl isocyanate or cyclohexyl isocyanate the respective products will be 5-(3-phenylureido)-3-methyl-pyrazole and 5-(3cyclohexylureido)-3- methylpyrazole.

Dimerization of propionitrile will yield 2-cyano-3- amino-2-pentene. When an equivalent amount of this material is used in place of B-aminocrotonitrile in the procedure of Example 1, 5-amino-3-ethyl-l ,4-

dimethylpyrazole will be produced This pyrazole can' be reacted with an isocyanate according to the procedures of Examples 3 or 8, infra. If the isocyanate is phenyl isocyanate, the product will be 5-(3-phenylureido)-3-ethyl-l ,4-dimethylpyrazole.

EXAMPLE 2 Preparation of 5-amino-4-bromo-l ,3-dimethylpyrazole Eleven and one-tenths parts dimethyl-pyrazole is dissolved in a mixture of parts of acetic acid and 10 parts of sodium acetate. Thereafter, 16 parts of bromine is added slowly to the solution while maintaining good agitation. After the bromine addition is complete, the material is poured onto about 300 parts of crushed ice. The mixture is made slightly alkaline with aqueous ammonia and then extracted with methylene chloride. Upon drying with anhydrous magnesium sulfate and removal of the solvent under reduced pressure, 5-amino-4-bromo-l ,3- dimethylpyrazole is recovered as a heavy oil. The compound has the following structure:

l i ll Br EXAMPLE 3 Preparation of 5-( 3-phenylureido )-4-bromol ,3-dimethylpyrazole One part of 5-amino-4-bromo-l,3-dimethylpyrazole from ethanol. The product recovered is 5-(3-' phenylureido )-4-bromo-l ,3-dimethylpyrazole having a melting point of about 220C. and the following structure:

I O H N \N l H l N Br OH;

EXAMPLES 4-7 The following isocyanates when substituted in the amounts indicated for phenyl isocyanate in the procedure of Example 3 react to give the product indicated.

of S-amino-l ,3-

Example Isoeyanate Parts Product 4 m-Chlorophenylisoeyanate 2.5 Cl H (12H;

H l N @gf \N WW A W UM 7 B1'-|-LCH:|

-[3-(4-ehlorophenyl)ureid01-4-bromo-t,3-dlmethyl- V 9 u W. 5 o-Frbmop'tieifyl'lsdeyeriateiJL.'L.'. .'.-L-. 2.7 Br 0 H (EH, ll l N m w BT--CH3 5-[3-(2-bromophenyDureldol-Qbromo-l,3-dimethyl- ...i,. py zot h w a I 6 o-Fluorophenylisoeyanate 2.2 F o H (3H ll l N @gq \N V Br--- CH3 5-[3-(2-fiuorophenyl)ureldol-t-bromb-l,3-dlmethylt r P a a it 7 p-Tolylisoeyanate 2.2 CH5 It. ll

EXAMPLE 8 Preparation of S-(3-cyclohexylureido)-l,3-dimethyl pyrazole EXAMPLE l3 Preparation of S-[ 3-( 2-fluorophenyl)ureido]-l ,3-dimethyl-4- chloropyrazole Six parts I of 5-| 3-(2-flu0rophenyl)ureidol-l ,3- dimethylpyrazole is dissolved in a warm solution of 4 parts of sodium acetate and 200 parts of acetic acid.

Three and one-half parts of sulfuryl chloride is added to the solution which is then agitated for 15 minutes. The mixture is poured into 500 parts of ice water. Pre- @l- -wr CH O H l a crpitated solids are collected by filtration and recrystal- C l; lization from methanol. The recovered compound has l a melting point of 210C. and the following structure:

CH3 EXAMPLES 9-12 O H 1 The following isocyanates when substituted in the l amounts indicated for cyclohexyl isocyanate in the pro- I cedure of Example 8 react to give the product indi- CH: cated. V g M W V 7 01 Example Isocyanate Parts Product 9 m FluoropTienylisocyanate 1 0 F 0 H tIJH 1 I N @e- N 5[3-(3-fluorophenyl)ureido]-1,3-dimethylpyrazole. l0 3,4-dichlorophenylisoeyauate 5.7 Cl 0 H (3H3 II I N 5-[3-(3,4-dichlorophenyD-ureido]-1,3-dimethy1pyrazole. 11 m-Nitrophenylisoeyauate 5.1 I|-I0z O H (1H I H l 5-I3-(3-nitrophenyl)ureido]-1,3-dimethylpyrazole.

l2 o-Bromophenylisoevanate 6.0 l|3r 0' H OH;

5-l3-(2-bromophenyl )ur idol-l,3-dimetliylpymzole.

EXAMPLE l4 Preparation of I 5 3-methyl-3-phenyl-ureido)-l ,3-dimethylpyrazole Eleven and one-tenth parts of 5-amino-l ,B-dimethylpyrazole is dissolved in a mixture of 200 parts of henzene and parts of pyridine. Seventeen parts of N-methyl-N-phenylcarbamoyl chloride is added and CH: O r

CHa

UTILITY The compounds of this invention are useful as plant .defoliants and accordingly can be used to cause the leaves to drop from numerous plants. This ability to cause leaves to drop is most useful on plants such as cotton, soybeans, seed alfalfa, and dry beans before harvest. The compounds also retard the rate of regrowth of the defoliated plants.

The amount of compound required for optimum effects will depend on the particular crop and environment under which it is growing. Within the meaning of this case, the amount of compound necessary to accomplish defoliation will be termed an effective amount. Normally, the rate at which the compound is applied will range from 0.25 to 15.0 kilogram per hectacre. One skilled in the art will be able to select the appropriate rate of application for any particular situation. Two or more ureidopyrazoles of this invention can be applied at the same time, if desired.

Compositions The compounds of the present invention can be used in the form of compositions which are prepared by admixing at least one of the active compounds with an inert diluent, such as pest control adjuvants or modifiers, to provide compositions in the form of dusts, water-dispersible powders, high-strength concentrates, and aqueous or organic dispersions. Thus, the compounds of this invention can be used with a carrier or diluent agent such as a finely divided solid, an organic liquid, water, a wetting agent, a dispersing agent, an

emulsifying agent, or any suitable combination of these.

The compositions, especially liquids and wettable powders, may contain as a conditioning agent one or agents as have heretofore been generally employed in plant control compositions of similar type. Suitable surface-active agents are set forth, for example, in Detergents and Einulsifiers" 1968 Annual by John W., q

ity of the components used separately. When used at higher rates it is preferred that the surfactant be present in the range of one-fifth to five parts surfactant for each one part of active agent.

i A. wettable Powders wettable powders are water-dispersible compositions containing the active material, an inert solid extender, and one or more surfactants to provide rapid wetting and prevent heavy flocculation when suspended in water.

The inert extenders which are preferred for use in the wettable powders of this invention containing the active compounds are of mineral origin.

The classes of extenders suitable for the wettable powder formulations of this invention are the natural clays, diatomaceous earth, and synthetic mineral fillers derived from silica and silicate. Most preferred fillers for this invention are kaolinites, attapulgite clay, montmorillonite clays, synthetic silicas, synthetic magnesium silicate, and calcium sulfate dihydrate.

Suitable surfactants for use in such compositions are those listed in Detergents and Emulsifiers 1968 Annual by J. W. McCutcheon, lnc. Among the more preferred surfactants are the non-ionic and anionic type, and those most suitable for the preparation of the dry, wettable products of this invention are solid forms of compounds known to the art as wetters and dispersants. Occasionally a liquid, non-ionic compound classified primarily as an emulsifier may serve as both wetter and dispersant.

Most preferred wetting agents are alkylbenzeneand alkylnaphthalenesulfonates; sulfated fatty alcohols, long-chain acid esters of sodium isethionate; esters of sodium sulfosuccinate; sulfated or sulfonated fatty acid esters;'petroleum sulfonates; sulfonated vegetable oils; and ditertiary acetylenic glycols. Preferred dispersants are methylcellulose, polyvinyl alcohol, lignin sulfonates, polymeric alkylnaphthalenesulfontates, polymethylene bisnaphthalenesulfonate, and sodium N-methyl-N-(long chain acid)taurates.

Wetting and dispersing agents in these preferred wettable powder compositions of this invention are usually present at concentrations of from about 0.5 weight per cent to 5 weight per cent. The inert extender then completes the formulation. Where needed, 0.1 weight per cent to 1.0 weight per cent of the extender may be replaced by a corrosion inhibitor or an anti-foaming agent or both.

Thus, wettable powder formulations of the invention will usually contain from about 25 to weight per cent active material, from 0.5 to 2.0 weight per cent wetting agent, from 0.25 to 5.0 weight per cent dispersant, and from 9.25 to 74.25 weight per cent inert extender, as these terms are described above.

When the wettable powder contains a corrosion inhibitor or an anti-foaming agent or both, the corrosion inhibitor will not exceed about one per cent of the composition, and the antifoaming agent will not exceed about 0.5 per cent by weight of the composition, both replacing equivalent amounts of the inert extender.

B. HIGH STRENGTH COMPOSITIONS AND AQUEOUS SUSPENSION CONCENTRATES High-strength compositions generally consist of 90 to 99.5 percent active ingredient and 0.5 to percent of v a liquid or solid surfactant such as those described in Detergents and Emulsifiers 1968 Annual by J. W. McCutcheon, Inc. Up to approximately half of the surfactant may be replaced by an anti-caking agent such as a synthetic silica. Such high-strength compositions can often be used in a manner similar to the wettable powders but they are also suitable for further formulation.

The aqueous suspension concentrates are prepared by mixing together and sandgrinding an aqueous slurry of water-insoluble active ingredient in the presence of dispersing agents. Thus, there is obtained a concentrated slurry of very finely divided particles in which the active ingredient is substantially all below 5 microns in size. This concentrated aqueous suspension is characterized by its extremely small particle size so that upon diluting and spraying, a very uniform coverage is obtained.

These aqueous suspension concentrates will contain from 15 to 55 percent of active ingredient, from to' 70 percent water with the remainder made up of surfactants, corrosion inhibitors, and suspending agents.

Suspensions in organic liquids can be prepared in a similar manner such as by replacing the water with mineral oil.

C. DUSTS Dusts are dense powder compositions which are in tended for application in dry form and are characterized by their free-flowing and rapid settling properties so that they are not readily windbome to areas where their presence is not desired. They contain primarily an active material and a dense, free-flowing, solid extender.

Their performance is sometimes aided by the inclusion of a wetting agent, and convenience in manufacture frquently demands the inclusion of an inert, absorptive grinding aid. For the dust compositions of this invention, the inert extender may be either of vegetable or mineral origin, the wetting agent is preferably anionic or non-ionic, and suitable absorptive grinding aids' are of mineral origin.

Suitable classes ofinert solid extenders for use in the dust compositions are thoseorganic or inorganic powders which possess high bulk density and are very freeflowing. They are also characterized by possessing relatively low surface areas and are poor in liquid absorption. Suitable classes of grinding aids are natural clays, diatomaceous earths, and synthetic mineral fillers derived from silica or silicate. Among ionic and non-ionic wetting agents, the most suitable are the members of the group known to the art as wetting agents and emulsifiers. Although solid agents are preferred because of ease in incorporation some liquid non-ionic agents are also suitable in the dust formulations.

Preferred inert solid extenders for the dusts of this invention are micaceous tales, pyrophyllite, dense kaolin clays, tobacco dust and ground calcium phosphate rock such as that known as Phosphodust."

Preferred grinding aids are attapulgite clay, diatomaceous, silica, synthetic fine silica and synthetic calcium and magnesium silicates. Preferred wetting agents are those previously described-under wettable powder formulations.

The inert solid extenders in the dusts of this invention are usually present in concentrations of from about 30 to weight per cent of the total composition. The grinding aid will usually constitute 5 to 50 weight per centof the composition, and the wetting agent will constitute from about 0 to 1.0 weight per centof the composition. Dust compositions can also contain other surfactants such as dispersing agents in concentrations of up to about 0.5 weight per cent.

The wettable powders described above can also be used in the preparation of dusts. While such wettable powders could be used directly in dust form, it is more advantageous to dilute then by blending with the dense dust diluent. In this manner, dispersing agents, corrosion inhibitors, and anti-foam agents may also be found as components of a dust.

Thus, the dust compositions of this invention will usually comprise about 5 to 20 weight per cent active material, 5 to 50 weight per cent absorptive filler, 0 to 1.0 weight per cent wetting agent, and about 30 to 90 weight per cent dense, free-flowing dust diluent, as these terms are used herein. Such dust formulations can contain, in addition, minor amounts of dispersants, corrosion inhibitors, and anti-foam agents, derived from the wettable powders used to make the dusts.

The following examples illustrate the use of the compounds and compositions of this invention. Unless otherwise stated, parts are parts by weight.

EXAMPLE l5 5-( 3'phenylureido)-l ,B-dimethylpyrowle 84.0% Attapulgite clay 7.5% Magnesium carbonate 2.0% Sodium lignin sulfonate l.5% Finely divided synthetic silica 2.0% Sodium alkylnaphthalenesulfonate 3.0%

The above ingredients are blended, micropulverized to a particle size essentially below 50 microns and reblended.

One kilogram of 5-( 3-phenylureido )-l ,3- dimethylpyra-zole formulated as above is suspended in 200 liters of water and applied to a hectare of cotton on which the bolls are open and ready to pick. The treatment accomplishes complete defoliation within l0 days and the cotton can then be machine harvested without contamination with trash or without leaf stains. The treatment also prevents regrowth of the defoliated plants until they are harvested.

The following compounds can be formulated and applied in the fashion of Example 15 with similar results.

5-[ 3-( 3-fluoro-4-chlorophenyl)ureido1-l ,3-

dimethylpyrazole 5-[3-(3-fluoro-4-methylphenyl)ureido1-l ,3-

dimethylpyrazole 5-[3-(3-fluorophenyl)ureido1-4-chloro-l,3-

dimethylpyrazole dimethylpyrazole 5-[3-(4-fluorophenyl)ureido]-1 ,3-dimethylpyrazole Ill ' EXAMPLE l6 3-( 2-fluorophenyl )ureido]-4-chlorol ,3-

dimethyl yrazole 25.0% Montmoril onite clay 69.0% Finely divided synthetic silica 2.0% Calcium li nin sulfonate 3.0% Dioctyl ium sulfosuccinate 1.0%

EXAMPLE l7 5-[ 3-( 3-fluorophenyl )ureidoll ,3-

- dimethylpyrazole 95.0% Trimethylnon loxy lyethoxyethanol 2.0% Finely dlvid synt etlc silica 3.0%

The above ingredients are blended, micropulverized to pass a 0.25 mm. screen and reblended. This formulation is suitable for further formulation or can be applied directly.

Two kilograms of 5-[3-(3-fluorophenyl)ureido]-l,3- dimethylpyrazole as formulated above are suspended in 200 liters of water containing 0.5 percent Triton X-100 wetting agent (octyl phenoxy polyethoxyethanol) and sprayed on a hectare of cotton two weeks before harvest is planned. The treatment causes rapid defoliation of the cotton plants, the bolls dry and the lint is easily picked by machine two weeks after treatment. The treated area yields clean high quality lint.

EXAMPLE l8 5-( 3-cyclohexylureido)-l ,4-dimethyl-3- ethylpyrazo e 30.0% Calcium lignin sulfonate and wood sugars 15.0% Hydrated attapulgite 1.5% Sodium pcntachlorophenate 0.5% Sodium carbonate 1.0% Water 52.0%

The above solid ingredients are micropulverized to pass a 0.59 mm. screen, mixed with the water and sandground to a particle size essentially below 5 microns.

A suspension containing 4 kilograms of 5-(3- cyclohexylureido)-l ,4'dimethyl-3-ethylpyrazole as formulated above and 150 liters of water containing 0.25 percent Triton B 1956 wetting agent (modified phthalic glycerol alkyd resin) is sprayed on a hectare of dry beans two weeks before harvest is planned. The pods are full and about ready for harvest but not dry. The treatment defoliates the plants and allows the bean pods to dry. When harvested they shell cleanly with a minimum of cracked or lost seed.

EXAMPLE l9 5-[ 3-( 3,4 dichlorophenyl)ureidoll -ethyl-3- The active compound is micropulverized to pass an 0.59 mm. screen and is then blended with other ingrelint.

dients and sand-ground to a particle size essentially below 5 microns. The resulting suspension can be emulsified into water.

Three kilograms of v 5-[3-(3,4- dichlorophenyl)ureido]- l -ethyl-3-methyl-4- chloropyrazole formulated as described above are suspended in 300 liters of water and sprayed on a hectare of soybeans two weeks before harvest is planned. The treatment defoliates the plants and allows the pods to, dry. The dry pods combine easily and cleanly and there are a minimum of beans lost in harvesting.

EXAMPLE 20 5-(3-methyl-3-phenylureido)-3=methyl pyrazole 50.0% Kaolinite 47.0% Methylcellulose l .0% Sodium alkylnaphthalenesulfonate 2.0%

The above ingredients are blended, micropulverized to a particle size essentially below 50 microns and reblended.

A suspension containing 2 kilograms of 5-(3-methyl- 3-phenylureido)-3-methylpyrazole and 300 liters of water containing 0.25 percent Tween 20 wetting agent is prepared. This is sprayed on a hectare of seed alfalfa when the seeds are full but not dry. The treatment defoliates the plants rapidly and makes it possible to harvest the seed with a minimum of loss.

EXAMPLE 21 5-[ 3-( S-nitrophenyl )ureidol-l ,3-dimethyl-4- chloropyrazole 50.0% Diatomaceous silica 44.5% Sodium lauryl sulfate 2.0% Finely divided synthetic silica 2.0% Partially desulfonated sodium lignin sulfonate 1.5%

The above ingredients are blended, air-milled to a particle size essentially less than 20 microns and reblended.

Five kilograms of 5-!3-(3-nitrophenyl)urcidol-l ,3- dimethyl-4-chloropyramle formulated as shown above are suspended in 200 liters of water containing 0.5 percent Triton X-lOO wetting agent and sprayed on a hectare of cotton three weeks before harvest is planned. The treatment defoliates the cotton and retards regrowth until the crop is harvested. When harvested the crop gives a good yield of clean, unstained, high quality I claim:

1. A method of defoliating plants comprising applying to said plants an effective amount of at least one compound having the formula R o H wherein:

R is hydrogen, methyl, ethyl, or phenyl; R, is cyclohexyl or wherein:

A is hydrogen, fluoro, chloro, bromo, or methyl, and B is hydrogen, chloro, or nitro; R; is hydrogen or methyl;

X is hydrogen, methyl, bromo, or chloro; and

Y is methyl or ethyl.

2. The method of claim 1 in wh 3-phenylureido)-l ,3-dimethylpyrazole.

ich said compound is 3. The method of claim 1 in which said compound is 5-[3-(2-fluorophenyl)ureido1-4-chloro-l ,3-

dimethylpyrazole.

4. The method of claim 1 in which said compound is 5-[ 3-( 3-fluorophenyl)ureido]-l ,3-dimethylpyrazole.

5. A composition for defoliating plants comprising an inert carrier and an effective amount of at least one compound having the formula s R O H I wherein:

R is hydrogen, methyl, ethyl, orphenyl; R is cyclohexyl or wherein:

A is hydrogen, fiuoro, chloro, bromo, or methyl, and B is hydrogen, chloro, or nitro;

R is hydrogen or methyl;

X is hydrogen, methyl, bromo, or chloro; and

Y is methyl or ethyl.

6. The composition of claim 5 in which said com-- 

2. The method of claim 1 in which said compound is 5-(3-phenylureido)-1,3-dimethylpyrazole.
 3. The method of claim 1 in which said compound is 5-(3-(2-fluorophenyl)ureido)-4-chloro-1,3-dimethylpyrazole.
 4. The method of claim 1 in which said compound is 5-(3-(3-fluorophenyl)ureido)-1,3-dimethylpyrazole.
 5. A composition for defoliating plants comprising an inert carrier and an effective amount of at least one compound having the formula
 6. The composition of claim 5 in which said compound is 5-(3-phenylureido)-1,3-dimethylpyrazole.
 7. The composition of claim 5 in which said compound is 5-(3-(2-fluorophenyl)ureido)-4-chloro-1,3-dimethylpyrazole.
 8. The composition of claim 5 in which said compound is 5-(3-(3-fluorophenyl)ureido)-1,3-dimethylpyrazole. 